C++ decimal point output format of instance code

In the classic introduction to algorithmic racing 1

Problem sets 1-5 discount (discount)

B: it's 95 yuan per dress. You can get a 15% discount if you spend more than 300 yuan. Input the number of pieces of clothes, output the amount to be paid (unit: yuan), and keep two decimal places.

The code I wrote is

#include<iostream>
#include<iomanip>
using namespace std;
int main(void){
  double s;
  cin>>s;
  
  if(s*95>=300){
    cout<<setiosflags(ios::fixed)<<setprecision(2)<<s*95*0.85<<endl;
  } 
  
  else{
    cout<<setiosflags(ios::fixed)<<setprecision(2)<<s*95<<endl;
  }
  
  
  return 0;
}

So I looked up how to display decimals in different formats in C++ :

Floating point output can be changed with
<< setiosflags( ios::fixed ) : never use scientific notation // Never use scientific notation. 
<< setiosflags( ios::scientific ) : always use scientific notation // Use scientific notation. 
<< resetiosflags( ios::floatfield ) : restores default (use fixed or scientific notation based on the precision)// Reset to the default. 
<< (re)setiosflags( ios::showpoint ) : controls if the trailing zeros and decimal point will be output (default is no) // Controls whether the zero after the decimal point is displayed. 
<< setprecision( digits ) : if fixed or scientific format is selected, controls the number of digits after the decimal place, otherwise controls the total number of significant digits//  if fixed or scientific Once determined, control the number of digits behind the decimal point; Otherwise, control all digits. 

#include <iostream>
#include <iomanip>
using namespace std;

int main(void){
  double S = 0.000000123;
  double A = 456.7;
  double B = 8910000000000.0;

  cout << "default precision is "
     << cout.precision() << endl;  // 6

  cout << "  S = " << S << endl;  // 1.23e-07
  cout << "  A = " << A << endl;  // 456.7
  cout << "  B = " << B << endl;  // 8.91e+12

  cout << setiosflags(ios::showpoint)
     << "ios::showpoint ON" << endl;

  cout << "  S = " << S << endl;  // 1.23000e-07
  cout << "  A = " << A << endl;  // 456.700
  cout << "  B = " << B << endl;  // 8.91000e+12

  cout << resetiosflags(ios::showpoint)
     << "ios::showpoint OFF" << endl;
  cout << setiosflags(ios::fixed)
     << "ios::fixed ON" << endl;

  cout << "  S = " << S << endl;  // 0.000000
  cout << "  A = " << A << endl;  // 456.700000
  cout << "  B = " << B << endl;  // 8910000000000.000000

  cout << resetiosflags(ios::fixed)
     << setiosflags(ios::scientific)
     << "ios::scientific ON" << endl;

  cout << "  S = " << S << endl;  // 1.230000e-07
  cout << "  A = " << A << endl;  // 4.567000e+02
  cout << "  B = " << B << endl;  // 8.910000e+12
}

The output is:

default precision is 6
S = 1.23e-007
A = 456.7
B = 8.91e+012
ios::showpoint ON
S = 1.23000e-007
A = 456.700
B = 8.91000e+012
ios::showpoint OFF
ios::fixed ON
S = 0.000000
A = 456.700000
B = 8910000000000.000000
ios::scientific ON
S = 1.230000e-007
A = 4.567000e+002
B = 8.910000e+012

--------------------------------

Process exited after 0.02482 seconds with return value 0

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